1. Field of the Invention
The present invention relates to a method of designing a tire profile. More particularly, the present invention relates to a method of designing a profile in the vicinity of a buttress of a tire.
2. Description of the Related Art
A tire comprises a tread, a shoulder linked to the tread, a adjustment portion linked to the shoulder, and a sidewall linked to the adjustment portion. The sectional shape of the shoulder is arcuate and has an upper end provided in contact with the end of the tread. The adjustment portion is usually flat. In other words, the sectional shape of a general adjustment portion is straight. The adjustment portion has an upper end provided in contact with the lower end of the shoulder. The sectional shape of the upper part of the sidewall is arcuate and has an upper end provided in contact with the lower end of the adjustment portion. The shoulder and the adjustment portion are also referred to as a buttress. There is also a tire in which a adjustment portion is not flat. A tire having no adjustment portion is also present.
The profile of a tire influences the basic performance of the tire, for example, a handling stability or a ride comfort. It is necessary to determine a proper profile corresponding to the concept of the tire. Japanese Laid-Open Patent Publication No. 2002-301916 has disclosed a method of determining a tread profile using an involute function.
In respect of the basic performance of the tire, a profile in the vicinity of the buttress is also important. A designer specifies the numeric values of a radius of curvature of the shoulder, an inclination angle of the adjustment portion, a length of the adjustment portion and a radius of curvature of an upper sidewall in order to reflect his (her) own designing thought. In order to achieve these numeric values, CAD software or FEM software is used to determine a profile. For the determination, trial and error are repeated. A long time is required for designing the profile. As a result of the trial and error, it is found that the specified numeric values cannot be achieved in an actual tire in some cases. In these cases, the numeric values are specified again, and furthermore, the trial and error is repeated.
It is an object of the present invention to provide a designing method capable of easily obtaining a profile in the vicinity of a buttress.